This application relates to a flow meter, and more specifically to dynamic calibration of a flow meter of a beverage brewing apparatus.
A plurality of factors influence the flavor when brewing a cup of coffee, including the quantity of coffee, the quantity of water, the temperature of the water, and the contact time between the coffee and the water. In many systems configured to brew a beverage such as coffee, a flow meter is used to monitor a volume of water delivered to the coffee. The flow meter generally includes a rotor having opposing polarity magnets embedded therein. The rotor is configured to spin about a central axis as water flows there through. As the flow meter rotates, these magnets pass a Hall Effect sensor, functioning as a switch that it activated and deactivated by the magnetic fields of the magnets. For every rotation of the rotor, a high and low signal is observed by the Hall Effect sensor.
Under constant conditions, a high quality flow meter may be accurate to within 0.5%, meaning that each toggle in the flow meter signal can be related directly to a volume of water. For example, if a system intends to deliver 1000 mL of water and the flow meter is calibrated to deliver 0.5 mL per pulse, a controller will simply track the total number of pulses until 2000 pulses have been observed. Accuracy of these systems is dependent upon the linearity of the flow meter over the operating range of the system. In order to control the operation conditions of a beverage brewing system a pump is typically used to control the flow rate. However, in systems where the operating conditions are not controlled, the flow rate of fluid through the flow meter may change based on variates in the wall voltage, boiler power, boiler efficiency, water temperature, or other influencing factors. As these factors shift the flow rate away from the nominal target rate, the performance of the flow meter similarly shifts, thereby compromising the accuracy of the system.